FUNDING has been provided to CTAHR for this research from the USDA Cooperative State Research, Education, and Extension Service Project HAW00121-1017S.

OBJECTIVES

The objective of this research is to study the effects of radiation mitigation by shade provided by trees that provided by novel and passive shade treatment alternatives. The long term goal is to develop sustainable coffee agroecosystems to enhance the niche market and sustainability of an expanding coffee industry in Hawaii. For this phase of the research, we will investigate how the tree and artificial shade treatments affect: (1) the microenvironment of the coffee agroecosystem, (2) the water relations and photosynthesis of the coffee plants, (3) soil nutrient availability and coffee nutrition, and (4) bean production and quality attributes-physical, chemical and organoleptic.

APPROACH

This study will employ a partial factorial design in which coffee variety and shade treatment will be crossed at 3 different sites. The two varieties of coffee are Guatemalan and yellow Catuai, an unimproved landrace and a hybrid bred for full-sun exposure, respectively. One site is in Waimanalo (Oahu) and represents the wettest location with the greatest natural cloud cover. Another site is near Kunia (Oahu) and is the driest and sunniest site. The third site is in Kona (Hawaii) and is a relatively dry site that receives regular afternoon cloud cover. The Guatemalan variety is present at all 3 sites. The Yellow Catuai is present only at the Waimanalo site. Two types of artificial shade cloth: black and aluminized, and a spray-on shade consisting of a kaolinite slurry will be utilized at all three sites. Tree shade is present at the Kona site. We hypothesize that shade effects on the microenvironment will lead to changes in coffee photosynthesis, water use, nutrition, growth and bean yield, and coffee quality. Thus, we will measure 1) microenvironmental components, including light, temperature, and relative humidity inside and outside the treatment areas and at different positions within the coffee plant canopy; 2) photosynthesis and leaf water use on individual coffee plants; 3) soil nutrient availability and coffee leaf nutrient content; 4) plant growth rate and green bean yield; 5) organoleptic and biochemical properties of dried and roasted beans.

The goal of this project is to evaluate shade effects on coffee productivity, bean biochemistry, and cup quality. Different shade alternatives and shade levels are being tested for their impact on important aspects of agroecosystem productivity and product quality. Over the past 2 years, we have harvested the coffee cherry after imposition of the shade treatments. These results are summarized as follows: Productivity: First year harvest results show a near-significant effect of the shade treatments on coffee yields. The yields of the kaolinite spray-on shade were slightly higher than full-sun yields. Shade coffee yields, whether under shade cloth or tree shade, were lower. Macadamia tree shade is 90% or more, much higher than the 40% shade levels of the shade cloth and target shade for the kaolinite spray. Second-year results so far are significant, showing a divergence of coffee yields among the treatments. The kaolinite spray-on shade treatment yields are the highest among the treatments. Full sun is next, followed by shade cloth. The coffee plants under macadamia tree shade failed to produce significant amounts of fruit. Leaf characteristics: Leaf morphology under shade matches predictions: chlorophyll, N, and specific leaf mass are all lower under shade. However, leaves of plants under kaolinite spray are similar to full sun leaves. All shade levels reduce leaf temperature by 3-5 degrees C. Photosynthetic rates of leaves under kaolinite shade is higher than full sun leaves. Coffee quality: Green bean size is generally larger under shade than full sun. The effect of shade on organoleptic properties for a specific size bean are small but sometimes significant. There is no consistent effect of treatment on taste preference. Biochemistry: The biochemical profiles of the green beans are all highly distinct, with only a few chemicals needed to significantly distinguish treatments and locations from each other.

The kaolinite shade provides a cost-effective means to increase yields of coffee in sub-optimal growing areas without disrupting mechanical operations or requiring greater inputs. This is achieved through reduced leaf stress and greater photosynthesis under full sun exposure. The effects on coffee cup quality and preference appear to be minimal; thus, our project may show that shade has no importance for coffee quality per se. A greater proportion of larger beans may increase market preference and thus command a higher price per pound, but this must be offset by lower yields for traditional shade treatments. The distinct biochemical profiles offer a potential tool for authenticating the origin and growing conditions for various coffees. If profiles are developed for specific growing regions and shade or other management conditions, then coffees being sold or marketed as such can be compared to these standard profiles. This has not been tested with respect to coffee blends, but the potential exists to authenticate different blend ratios, as well.

PUBLICATIONS (not previously reported): 2003/10 TO 2006/09

1. Gautz, Loren D., Steiman, Shawn R., Jackson, Mel C., Bittenbender, Harry C., Idol, Travis W. 2006. Shade Coffee In Hawaii: Preliminary Economic Impact Of Creating Shade For Culture Of Coffee. Abstract Published In 21st International Conference On Coffee Science, Association Scientifique Internationale Du Cafe, September 11th-15th, 2006, Montpellier, France.

2. Jackson, Mel C., Steiman, Shawn R., Gautz, Loren D., Bittenbender, Harry C., Idol, Travis W. 2006. Quality Determination And Group Iscrimination Of Shade Grown Coffee Using Solid Phase Microextraction. Abstract Published In 21st International Conference On Coffee Science, Association Scientifique Internationale Du Cafe, September 11th-15th, 2006, Montpellier, France.

3. Steiman, Shawn R.; Bittenbender, Harry C.; Idol, Travis W.; Gautz, Loren D.; Jackson, Mel. C. 2006. Shade Coffee In Hawaii-The Impact Of Light On Coffee Quality. Abstract Published In 21st International Conference On Coffee Science, Association Scientifique Internationale Du Cafe, September 11th-15th, 2006, Montpellier, France.

4. Steiman, Shawn R.; Idol, Travis W.; Bittenbender, Harry C.; Gautz, Loren D.; Jackson, Mel C. 2006. Physiological Response Of Coffee To Different Shading Regimes. Abstract Published In 21st International Conference On Coffee Science, Association Scientifique Internationale Du Cafe, September 11th-15th, 2006, Montpellier, France.